World Bulletin / News Desk
The monarch butterfly uses a magnetic compass to guide its extraordinary migration thousands of km across North America, scientists say.
Monarchs are known to possess a Sun compass that keep flying south towards Mexico even on cloudy days.
It was proven in a labratory experiment that when the magnetic field changes the butterflies also change their way of direction.
A study in Nature Communications suggests that like turtles and birds the insects have a geomagnetic compass.
The North American monarch butterfly Danaus plexippus is famous for its epic journey from Canada to Mexico.
Every Autumn, millions of the insects set off across Lake Erie and head south for the warmer forests of the Michoacan mountains.
"This is a marvellous piece of biology. It's like a work of art. It's inspiring and it can teach us important things about migrating animals," said Prof Steven Reppert of University of Massachusetts Medical School.
It was proven that the light-sensitive molecules in the antennae of the butterfies could calculate the position of the Sun.
By combining this with their inbuilt biological clock, they create a time-compensated Sun compass.
They demonstrated the butterflies ability by strapping them into a flight simulator, allowing them to point in any direction while flying "on the spot".
They surrounded the chamber with a magnetic coil system and varied the inclination angle of the field - effectively changing the position of the equator and the poles.
The monarchs responded by turning in the direction they perceived as south.
"To our knowledge, this is the first demonstration of the use of an inclination magnetic compass by a long-distance migratory insect," said Prof Reppert. ,
"It may serve as an important orientation mechanism when directional daylight cues are unavailable."
Learning how the monarchs perform their miracle could also aid their conservation.
"People are concerned - currently they are threatened by climate change, herbicides and the continuing loss of milkweed [their primary food source] and overwintering habitats," said Prof Reppert.
"We're used to seeing about half a billion butterflies at the overwintering sites. But last year it was probably two orders of magnitude lower."
And now there is new vulnerability to consider: "The potential disruption of the magnetic compass in monarchs by human-induced electromagnetic noise," said Dr Reppert.
He referred to a recent study of the European robin, which found that even weak electromagnetic fields from electrical devices and AM radios can apparently interfere with the birds' internal compass.Last Mod: 25 Haziran 2014, 12:40